We study the site percolation problem on square lattices with two kinds of
sites, which are assembled in such a way that the resulting structures have
patchwise topographies. Lattices formed by collections of either randomly
or orderly localized patches of different sizes are generated. The composit
ion of this system is: specified by two independient variables, p and q, wh
ich are the occupation probabilities of each type of patch. Interesting pha
se diagrams in (p,q) composition space for the percolative transition are o
btained and explained. [S1063-651X(99)07602-3].